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CHAPTER
DNA: The
Hereditary
Molecule
Chapter 1 • Modern Genetics for All Students
T1
CHAPTER 1
DNA: The Hereditary Molecule
CHAPTER 1 OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .T4
SECTION A
What is DNA? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S5 . . . . . .T5
Section A Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T6
1. An Introduction to DNA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S6 . . . . . . . T7
2. DNA in the News . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S8 . . . . . . . T8
SECTION B
What Does DNA Look Like? . . . . . . . . . . . . . . . . . . . . . . . . . . . . S9 . . . . .T11
Section B Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T12
1. Spooling Purified DNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S10 . . . . . . T13
2. Extracting DNA from Calf Thymus . . . . . . . . . . . . . . . . . . . . . S13 . . . . . . T15
SECTION C
What is the Structure of DNA? . . . . . . . . . . . . . . . . . . . . . . . . . S17 . . . . .T19
Section C Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T20
1. The Puzzle of DNA Structure and Replication . . . . . . . . . . . . . S18 . . . . . . T23
2. “The Spiral Staircase” from The Cartoon Guide to Genetics. . . S21 . . . . . . T29
3. What is a Model? And What is it Good For? . . . . . . . . . . . . . . S26 . . . . . . T29
4. Building a Three-Dimensional DNA Model . . . . . . . . . . . . . . . S27 . . . . . . T30
5. DNA Model Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S31 . . . . . . T32
6. DNA Word Search . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S32 . . . . . . T34
SECTION D
What Does DNA Do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S33 . . . . .T35
Section D Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T36
1. DNA Codes For Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S34 . . . . . . T37
2. “How DNA Codes for Proteins” from
The Cartoon Guide to Genetics . . . . . . . . . . . . . . . . . . . . . . . . S37 . . . . . . T37
3. The Gene Expression Dance. . . . . . . . . . . . . . . . . . . . . . . . . . . S48 . . . . . . T39
4. Paper Proteins: Models for Simulating Gene Expression . . . . . S49 . . . . . . T69
5. Using the Genetic Code to Translate an mRNA . . . . . . . . . . . . S51 . . . . . . T74
SECTION E
How Does DNA Determine a Trait? . . . . . . . . . . . . . . . . . . . . . . S53 . . . . .T77
Section E Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T78
1. An Introduction to the Connection Between Genes and
Visible Traits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S54 . . . . . . T80
2. Shine On! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T81
a. How to Read a Micropipettor . . . . . . . . . . . . . . . . . . . . . . . . S55 . . . . . . T84
b. Practicing Microbiological Techniques . . . . . . . . . . . . . . . . . S58 . . . . . . T87
c. Engineering Glow-in-the-Dark Bacteria . . . . . . . . . . . . . . . . S60 . . . . . . T92
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Chapter 1 Overview
THIS OPENING CHAPTER of Modern Genetics for all Students provides you with an
exciting opportunity to capture the interest of your students in what is undeniably one of
the most active and important aspects of modern biology: the study of our genes and the
ways they influence our lives from conception to death.
We will begin, not with stories of a monk puttering around with peas in his garden 150
years ago (important as that story about Gregor Mendel is in the history of biology).
Rather we will begin by giving the students an opportunity to view the substance that lies
at the very heart of biology: DNA. Before the first class session for the genetics section of
the course is over, your students will see with their own eyes that DNA is not just a theoretical abstraction, but a real, stringlike physical substance that one can actually wind up
on a wooden stick- and thereby prepare for more detailed study!
After helping you to capture their attention in this way, the chapter will help you move
them to progressively deeper levels of understanding of DNA structure and function with a
series of puzzle-solving, model-building, and simulation exercises. But then the high point
of the chapter will come at the end, when your students will become genetic engineers and
will use a piece of DNA to transform dull and ordinary bacteria into ones that glow in the
dark! Even more than the first exercise, the last one in this chapter should convince your
students that DNA is not just some sort of textbook abstraction that they should study in
order to pass future exams, but a vitally important substance that they owe it to themselves
to learn more about.
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CHAPTER 1
DNA: The
Hereditary
Molecule
SECTION A
What is
DNA?
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Chapter 1: Section A Background
LET’S GO! LET’S INTRODUCE your students to the exciting world of modern genetics
and get them motivated to learn more about it!
In Section A.1, a short and simple reading assignment will be used to introduce your students to very basic concepts regarding the role of DNA as the carrier of the hereditary
information that explains both the similarities and differences among human beings. In
Section A.2, your class will be challenged to begin collecting newspaper and magazine
articles about genetic research and controversies; this collection should reinforce the concept that DNA is extremely relevant to their everyday lives.
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A.1
An Introduction to DNA
STUDENT PAGES 6-7
LESSON OVERVIEW
This lesson is a student reading assignment designed to familiarize your students with the
general concepts underlying the study of DNA.
TIMELINE
It will take an average student 15 to 20 minutes to read this material. It could be assigned
as homework.
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A.2
DNA in the News
STUDENT PAGE 8
LESSON OVERVIEW
NO FIELD OF SCIENCE seems to get more press coverage these days than genetics, and
certainly no molecule is mentioned in the news more than DNA is. DNA evidence makes
the news with great regularity. It has been introduced as evidence in highly publicized
murder trials and is now regularly being used to reexamine the guilt or innocence of prisoners convicted of violent crimes many years ago. It is being used often to determine the
identity or the paternity of individuals who have been dead for a long time, and even is
being used to determine the nature of obscure fossilized plants or animals. Leading medical journals regularly call press conferences to make what some have begun to call their
‘gene of the month’ announcements: reports of newly identified genetic defects that are
thought to be responsible for breast cancer, mental illness, or some other serious human
condition. Certain other press reports express either optimism or pessimism about the
prospects for curing genetic ailments with gene therapy, and others deal with the controversies that surround the development of new kinds of genetically engineered plants or
animals, the labeling of genetically modified (GM) foods, and efforts to patent certain
human genes.
What better way to get your students to appreciate how much relevance the study of DNA
has for their own lives than by getting them involved in collecting and discussing such
news articles?
Your students will benefit most if they start collecting such news stories right away. Even
though they will not have a deep understanding of the basic principles of heredity or of
DNA structure and function, many of the articles they collect now will prove useful to
them later on, when they begin dealing with various aspects of human disease (Chapter 3)
and the ethical considerations related to DNA research (Chapter 4). It will undoubtedly
help your students to understand the kinds of articles they should look for if you have a
couple of interesting news clippings to read and discuss with them when you begin the
study of genetics. Then you can challenge them to get started searching for "DNA in the
News".
In order to sustain interest in this information-gathering project it will be important not to
ignore the articles that the students bring to class. However, you’ll probably want to avoid
devoting too much time to the articles when they first appear, particularly on days for
which you have a full period of activities scheduled. The following are some of the
approaches that other teachers have found useful:
• require students to turn in a very brief summary of each article that they have collected,
following either the guidelines given in the student pages or others that you provide;
• create a bulletin board on which students can post their articles after calling them to the
attention of the class with a simple one-sentence description;
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• set aside a short period each week for a discussion of the most interesting article(s) on
the bulletin board- if there are more articles on the bulletin board than can be discussed
in the time available, you may want to have the class vote to determine which article to
discuss;
• create a scrapbook in which the students may file their articles after they have been on
the bulletin board for some period of time — future students may find it instructive to
compare scrapbooks compiled different years to determine how much the hot topics in
genetics change from year to year.
Suggestions for various alternative ways that students might use these articles to produce a
capstone experience for their study of genetics will be made in Chapter 4.
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